diff --git a/AIStudyApp/AIStudyAppTests/MaterialPathResolverTests.swift b/AIStudyApp/AIStudyAppTests/MaterialPathResolverTests.swift
index a9db5af..9850aff 100644
--- a/AIStudyApp/AIStudyAppTests/MaterialPathResolverTests.swift
+++ b/AIStudyApp/AIStudyAppTests/MaterialPathResolverTests.swift
@@ -3,12 +3,38 @@ import XCTest
 
 final class MaterialPathResolverTests: XCTestCase {
 
-    // MARK: - materialTypeFrom (infer from apiType + title)
+    // MARK: - resolveKnowledgeSource path
 
-    func test_materialTypeFrom_knowledge_source_with_md_title_returns_markdown() {
-        let result = MaterialPathResolver.resolve(materialId: "m1", apiType: "knowledge_source", title: "note.md")
-        // Path won't exist, but we test the type inference via the file system cascade
-        XCTAssertNil(result) // File doesn't exist
+    func test_resolveKnowledgeSource_finds_file_in_knowledge_sources_dir() {
+        let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
+        let sourceId = "ks-test-\(UUID().uuidString)"
+        let ksDir = docs.appendingPathComponent("knowledge_sources/\(sourceId)")
+        try? FileManager.default.createDirectory(at: ksDir, withIntermediateDirectories: true)
+        let fileURL = ksDir.appendingPathComponent("content.md")
+        defer {
+            try? FileManager.default.removeItem(at: fileURL)
+            try? FileManager.default.removeItem(at: ksDir)
+        }
+
+        FileManager.default.createFile(atPath: fileURL.path, contents: "test".data(using: .utf8))
+
+        let result = MaterialPathResolver.resolve(materialId: sourceId, apiType: "knowledge_source", title: "content.md")
+        XCTAssertNotNil(result)
+        XCTAssertEqual(result?.filePath, fileURL.path)
+        XCTAssertEqual(result?.materialType, .markdown)
+    }
+
+    func test_resolveKnowledgeSource_returns_nil_for_empty_dir() {
+        let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
+        let sourceId = "ks-empty-\(UUID().uuidString)"
+        let ksDir = docs.appendingPathComponent("knowledge_sources/\(sourceId)")
+        try? FileManager.default.createDirectory(at: ksDir, withIntermediateDirectories: true)
+        defer { try? FileManager.default.removeItem(at: ksDir) }
+
+        // Empty directory → no files → falls through to Documents/Caches
+        let result = MaterialPathResolver.resolve(materialId: sourceId, apiType: "knowledge_source", title: "note.md")
+        // Directory exists but is empty → resolveKnowledgeSource returns nil → falls through
+        XCTAssertNil(result) // No file in Documents or Caches either
     }
 
     // MARK: - resolve returns nil for nonexistent file
@@ -26,11 +52,9 @@ final class MaterialPathResolverTests: XCTestCase {
 
     func test_resolve_finds_file_in_documents() {
         let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
-        let fileId = "test-resolve-\(UUID().uuidString)"
+        let fileId = "test-docs-\(UUID().uuidString)"
         let fileURL = docs.appendingPathComponent(fileId)
         defer { try? FileManager.default.removeItem(at: fileURL) }
-
-        // Create a temp file in Documents
         FileManager.default.createFile(atPath: fileURL.path, contents: "test".data(using: .utf8))
 
         let result = MaterialPathResolver.resolve(materialId: fileId, apiType: nil, title: nil)
@@ -45,7 +69,6 @@ final class MaterialPathResolverTests: XCTestCase {
         let fileId = "test-cache-\(UUID().uuidString)"
         let fileURL = cache.appendingPathComponent(fileId)
         defer { try? FileManager.default.removeItem(at: fileURL) }
-
         FileManager.default.createFile(atPath: fileURL.path, contents: "test".data(using: .utf8))
 
         let result = MaterialPathResolver.resolve(materialId: fileId, apiType: nil, title: nil)
@@ -53,28 +76,25 @@ final class MaterialPathResolverTests: XCTestCase {
         XCTAssertEqual(result?.filePath, fileURL.path)
     }
 
-    // MARK: - materialType inference via file cascade
+    // MARK: - materialType inference from title extension
 
-    func test_resolve_infers_type_from_title_extension() {
+    func test_resolve_infers_markdown_from_title() {
         let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
-        let fileId = "test-type-\(UUID().uuidString)"
+        let fileId = "test-md-\(UUID().uuidString)"
         let fileURL = docs.appendingPathComponent(fileId)
         defer { try? FileManager.default.removeItem(at: fileURL) }
-
         FileManager.default.createFile(atPath: fileURL.path, contents: "test".data(using: .utf8))
 
-        // .md title → markdown
-        let result = MaterialPathResolver.resolve(materialId: fileId, apiType: "knowledge_source", title: "doc.md")
+        let result = MaterialPathResolver.resolve(materialId: fileId, apiType: "temporary_file", title: "note.md")
         XCTAssertNotNil(result)
         XCTAssertEqual(result?.materialType, .markdown)
     }
 
-    func test_resolve_pdf_title_infers_pdf_type() {
+    func test_resolve_infers_pdf_from_title() {
         let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
         let fileId = "test-pdf-\(UUID().uuidString)"
         let fileURL = docs.appendingPathComponent(fileId)
         defer { try? FileManager.default.removeItem(at: fileURL) }
-
         FileManager.default.createFile(atPath: fileURL.path, contents: "test".data(using: .utf8))
 
         let result = MaterialPathResolver.resolve(materialId: fileId, apiType: "temporary_file", title: "book.pdf")
@@ -82,12 +102,49 @@ final class MaterialPathResolverTests: XCTestCase {
         XCTAssertEqual(result?.materialType, .pdf)
     }
 
-    func test_resolve_unknown_apiType_defaults_to_unknown_materialType() {
+    func test_resolve_infers_text_from_title() {
         let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
-        let fileId = "test-unknown-\(UUID().uuidString)"
+        let fileId = "test-txt-\(UUID().uuidString)"
         let fileURL = docs.appendingPathComponent(fileId)
         defer { try? FileManager.default.removeItem(at: fileURL) }
+        FileManager.default.createFile(atPath: fileURL.path, contents: "test".data(using: .utf8))
 
+        let result = MaterialPathResolver.resolve(materialId: fileId, apiType: "knowledge_source", title: "notes.txt")
+        XCTAssertNotNil(result)
+        XCTAssertEqual(result?.materialType, .text)
+    }
+
+    func test_resolve_infers_epub_from_title() {
+        let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
+        let fileId = "test-epub-\(UUID().uuidString)"
+        let fileURL = docs.appendingPathComponent(fileId)
+        defer { try? FileManager.default.removeItem(at: fileURL) }
+        FileManager.default.createFile(atPath: fileURL.path, contents: "test".data(using: .utf8))
+
+        let result = MaterialPathResolver.resolve(materialId: fileId, apiType: "temporary_file", title: "book.epub")
+        XCTAssertNotNil(result)
+        XCTAssertEqual(result?.materialType, .epub)
+    }
+
+    func test_resolve_infers_image_from_title() {
+        let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
+        let fileId = "test-img-\(UUID().uuidString)"
+        let fileURL = docs.appendingPathComponent(fileId)
+        defer { try? FileManager.default.removeItem(at: fileURL) }
+        FileManager.default.createFile(atPath: fileURL.path, contents: "test".data(using: .utf8))
+
+        for ext in ["png", "jpg", "jpeg", "webp"] {
+            let r = MaterialPathResolver.resolve(materialId: fileId, apiType: "knowledge_source", title: "photo.\(ext)")
+            XCTAssertNotNil(r)
+            XCTAssertEqual(r?.materialType, .image, "ext .\(ext) should infer .image")
+        }
+    }
+
+    func test_resolve_unknown_apiType_defaults_to_unknown() {
+        let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
+        let fileId = "test-unk-\(UUID().uuidString)"
+        let fileURL = docs.appendingPathComponent(fileId)
+        defer { try? FileManager.default.removeItem(at: fileURL) }
         FileManager.default.createFile(atPath: fileURL.path, contents: "test".data(using: .utf8))
 
         let result = MaterialPathResolver.resolve(materialId: fileId, apiType: "other_type", title: "file.bin")